Telephone repeating apparatus and circuit.



J. J. SKIDMORE.

TELEPHONE REPEATING APPARATUS AND CIRCUIT.

APPLICATION FILED MAYQ, 1907.

912,908. Patented Feb. 16, 1909.

-mnm i: I\S- i v aw '1 H 0%156515- "3 I I Inventor,

IoHN'LsKmMoRE, or BOJSTON, MAssIcHUsETrs AssIcNon To AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

TELERHONE REPEATING APPARATUS AND CIRCUIT.

Specification of Letters Patent.

Patented Feb. 16, 1909.

Application filed May 9, 1907. Serial No. 372,701.

To' all whom it may concern:

Be it known that I, JOHN J. SKIDMORE, residing at Boston, in the county of Suffolk and State of Massachusetts, have invented cer- 5 tain Improvements in Telephone Repeating Apparatus and Circuits, of which the follow- 111 is a specification.

Telephone repeating apparatus in practice is frequently included in the circuit connections of switchcords, thus securing a reinforcing action between whatever lines the cord may be used to unite. Since the lines will naturally not always be of the same length and character, the re eater is obviously often called upon to act etween sections of the complete circuit which differ materially as to their electrical properties. As is well known, in repeating circuits which are commercially 1 use, such, for example, as that disclosed in the patent, to Shreeve, No. 835,037, Novemher 6, 1906, it is necessary to have something a preaching an electrical balance between e line sections to prevent reactive disturbances between the receiving and transmitting elements of the apparatus. Instead of adjusting at the repeater the resistance and capacity of the sections which it connects, as described in the above-mentioned patent, the so-called singing of the apparatus may be prevented by somewhat decreasing its sensitiveness.

The purpose of the resent invention is to provide a system in w 'chthis' changein the condition of therepeater will be made when- 35. ever necessary'without attention uponthe 1 part of the switching operator.

The accompanying drawing illustrates diagrammatically a repeating apparatus included in a cord-circuit arranged'inaccordance with my invention.

U on a switchboard at a station A is situ-' ate switching means, which is here shown as consisting of the usual jacks, of which'four illustrated, these being designated by the characters J JJ and J. Thespringsg j of the acks are. connected to line or main conductors L and L, which may represent either ejnbstation ortrunk line constituting a sectron of the entire transmitting circuit. The

. .50 an m a or trunk lines are assnmed'to be of,

e pilwhfi .1 .5 j n to the a k J comparatively lon while those 91 themes J a d? ar muc s. 'e rn i Q c -hi s o n as }',9. teere mm n re ur by a conductor 10. In this conductor belonging to the jacks J and J are included resistances I, which will be hereinafter more particularly referred to.

Associated with the switchboard are a suitable number of connecting or cord circuits C adapted when in use -to constitute sections of complete transmitting circuits. Only one cord circuit is represented, this terminating in plugs P and I for cooperation with the jacks. The tips p and rings p of the plugs are connectedres ectively to conductors 11 and 12, while l' jetween the sleeves p extends a conductor 13. Included in the cord is a reinforcing apparatus and circuit, the other mechanisms usuallypresent in connecting circuits being omitted from the drawing to render the present invention more clear. In the strands 11 and 12 are the primary windings 'of a repeating induction coil M, which acts to deliver energy to the reinforein circuit. This coil has said primary win ings arranged in sections m 'm m and m, of which m and m are in the conductor 11, while sections we and m are in the conductor 12. In each air of sections the terminals other than t ose joined to the cord strands are united, and connected by abridge conductor 14, which contains thefprimary 0 of a regulating 1nduction coil 0, its secondary o bein' the third conductor 13of the cord.

windings of the induction coil 0 are preferably of comparatively low resistance. The seconda winding of the coil M is shown in sections 'm and m included in a circuit 15: closed through the winding of the receiving element 1' of the repeating a paratus R. The transmitting element 1' 0i therepeater forms a art of a circuit 16, which also contains a rimary winding In of a transmitting 1nattery B and. the

moth uction coil N, the sectional secondary n v of which is comprised'in the cord strands 11 and 12 at opposite sides of-the bridge 14;. This coil N returns reinforced energy t o the line, operatingin a man'ner now famn arto those slnlled in the art.

The third conductor 13 0f the cord contains a battery -B andflthe winding of 'a lows n i v r ay he net.-

tiire 18 and fro t contact of saidreia'y 130-.

a at qemp e tithe i t'lfi er he raasmit i em i Q1 he' peat e s n PQ EWP o h yatein, it should first be noted that if the short lines of jacl's J and J are connected to one another it will not be necessary to seek to reinforcc the voice currents, since transmission will he sulliciently good without this, and a switchcord not comprising a repeater may he used, so that my invention does not here come into play. If the lines joined are the longer ones J and J, the condition here encountered may he considered to be such'that the fluctuating terminal impedance has been offset by the line capacity, so that the im edance as a whole has become substantia ly constant. These lines are sufficiently balanced for the purposes of the herein-described re eatingapparatus. The operation will then e'as follows: When the operator places the plugs P and P in the jacl 's J and J a circuit is completed from ground to ground through the conductors 10 10, sleeve contacts of the jacl's, sleeves of the plugs, conductor 13 and winding of relay 17, resulting in the energization of the relay from the battery B". By attracting its armature this relay closes the circuit 16 of the transmittingelement1' and prepares the repeater for o eration. The normally open condition of t 1e circuit 16 prevents waste of the battery B, and the initial singing which would follow the condition of extreme unbalance if but one plug were placed in a jack, while the circuit of the transmitting element were closed. As there is no resistance in the conductors 16' of the jaci's, and as the winding of the relay 17 and secondary o of the induction coil O'are of low resistance, the total resistance of the grounded third con- I ductor circuit of the cord will be small.

through the coil section m and back by conductor 12 to line. The current in the pri mary sections m and m exercises an inductive effect upon the com anion rimary sections 'In and'm, as a resu t of. w oh the V0106 currents are transmitted to a certain extent directly through the, cord into the hne conductors of the jackJ. These pairs of primary windings are so connected that the current flowing in both sections of each pair is neutralized as regards its efi'ects upon the secondary winding, and therefore the only inductive action on the latter is from i the current traversing the bridge. The current generated thereby in the secondary energizes the receiving element of the repeatso slight as not to disturb transmission.

ing apparatus, which, operating the trans rmttmg element, causes the circuit 16 to throw upon the line through the coil N reinforcing currents from the battery B. On account of the length and consequent approximate balance of the connected lines, the extremities of the bridge conductor 14 are at the same potential with respect to the energy put upon the line by the secondary windings n of the transmitting induction coil and the reinforcing currents do not resaid bridge and the receiving element aretraversed by the reinforcing as well as the is to be joined to the rela-- originating current, tending to cause the apparatus to sing. But we now have in the circuit of conductor 13 the resistance 1, which is so selected that it bears some predetermined relation to the impedance of the line connected to its jack, the less the impedance the greater being the resistance.

This resistance in series with the secondary winding 0 of the coil '0 increases the impedance of its primary, so that less of'the original transmitted current traverses it. The reinforcing eflect of the repeating apparatus is therefore somewhat decreased, though notenough to materially impair its efficiency, and it is rendered less sensitive. This being true, the reactive effect upon it due to the lack of balance" of the lines 18 less, and, when this adjustment is properly provided for by inversely. proportionin the 1'e' sist'ance to'the 'impedance"'of the-line with which it is associated, the singing becomgs (3 will vhe seen that this control is made wholly incident to another act upon the 'part of the operator necessary to the switching of the lines, and as an adjustment requires no thou 'ht.

I c aim: 1. The combination of a telephone circuit or circuit section; telephone apparatus associated therewith; two other telephone 'cir-" cuits or circuit sections uhich are une ual or dissimilar with relation to each t er;

means for connecting the first named circuit with and dlsconnectlng 1t, from each of said two other c rcuits, and means assoc ated with one of said two unequal circuits adapted upon connection of its circuit with 'saidfirst named circuit to control the sensitiveness of the telephone apparatus associated therewith. e

2. A telephone systemcomprising lines,

and jacksto which they are JOlDBd; telephone apparatus which'may be associated with said lines; and a resistance connected to an element of a jack for cooperation uith said apparatus and bearing a predetemined relation to the line to which the jack belongs.

3. The combination of a telephone circuit or circuit section; telephone apparatus asso-' ciated therewith; two other telephone circuits or circuit sections uhich are unequal or dissimilar with relation to each other; a]

switchelement united to each of said circuits for connecting the first named circuit to either of the other two; and means connected to the s itch element of one of the two unequal circuits for varying the sensitiveness of the telephone apparatus of the to actuate the telephone apparatus; and

means adapted to be brought into cooperative relation vtith the bridge by connection of the two circuit sections and acting to vary the electrical impedance of the bridge.

5. The combination lib. two sections of a telephone transmitting circuit, of means for connecting and cisconnecting said sections; telephone apparatus associated \xith one of the sections; a brid e-across the last-named sect on through a rich current passes to actuate the telephone apparatus; and means permanently associated uith the other section adapted to be brou ht into cooperative relation with the bridge y connection of the two circuit sections and acting to vary the electrical impedance of the bridge.

6. .The combination u it-h two sections of a telephone transmitting circuit, of a plug and a' jack for connecting and disconnectin said sections tele hone apparatus associate uith the section airing the plug; a bridge across the last-named section through uhich current'passes to actuate the telephone apparatus; and a resistance permanent] connected to an element of the jack and a apted upon engagement of the plug with the jack to be brou ht into cooperative relation with the bridge and thereby vary the electrical impedance of said bridge, said resistance having a predetermined relation to the circuit section to the jack of which it is connected.

7. A telephone system comprising line circuit conductors and jacks to which they are joined; a connecting circuit having plugs for cooperating with the jacks and a bridge through which current passes to actuate the repeating apparatus; a repeating apparatus included in the connectin circuit; and a resistance associated wit a jack and adapted, by the insertion of a plu of the connecting circuit in said jack, to be brought into cooperative relation with the bridge to vary the impedance thereof.

8. The combination u it-h telephone lines and jacks to uhich. they are oined, the

sleeve contacts of said jacks being grounded,

of a three-conductor cord-circuit comprising plugs .for cooperation with the jacks; a repeating aptparatus included in the line strands of t e cord; a resistance included in the ground connection of a jack; and means contained in the third conductor of the cord for inductively associating the resist ance with the repeating circuit, substantially as described.

9. In a telephone system, the combination uith a transmitting circuit, of a reinforcing circuit; reinforcing apparatus associated with said reinforcing circuit; a bridge across the transmitting circuit, said bridge being adapted to carry current for the supply of energy to the reinforcing circuit;

and a resistance inductively associated uith the bridge to affect the sensitiveness of said reinforcing apparatus.

In testimony vshereof, I have signed my name to this specification in the presence of two subscribing witnesses, thisseventh day of May 1907.

JOHN'J. SKIDMORE.

Witnesses:

GEO. WILLIs PIERCE, JAMES E. LYNCH. 

